<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" Content="text/html; charset=Windows-1252">

<TITLE>Recovery volumes</TITLE>
<link href="style.css" rel="stylesheet" type="text/css">
</HEAD>

<BODY>

<P class="title"><A NAME="HELPArcRecVolumes"></A>Recovery volumes<hr></P>

<P>Recovery volumes or .rev files are special files which can be created
by WinRAR and allow to reconstruct missing and damaged files in a volume
set. They can be used only with <A HREF="HELPArcVolumes.htm">multivolume
archives</A>.</P>

<P>This feature may be useful for backups or, for example, when you
posted a multivolume archive to a newsgroup and a part of subscribers
did not receive some of the files. Reposting recovery volumes instead
of usual volumes may reduce the total number of files to repost.</P>

<P>Each recovery volume is able to reconstruct one missing RAR volume.
For example, if you have 30 volumes and 3 recovery volumes, you are
able to reconstruct any 3 missing volumes. If the number of .rev files
is less than the number of missing volumes, reconstructing is impossible.
Total number of usual and recovery volumes must not exceed 65535.
Number of recovery volumes must not be larger than tenfold amount
of RAR volumes. Values exceeding the threshold are adjusted automatically.</P>

<P>Original RAR volumes must not be modified after creating recovery
volumes. Recovery algorithm uses data stored both in REV files and
in RAR volumes to rebuild missing RAR volumes. So if you modify RAR
volumes, for example, lock them, after creating REV files, recovery
process will fail.</P>

<p>Additionally to recovery data, RAR 5.0 recovery volumes also store
service information such as checksums of protected RAR files. So they are
slightly larger than RAR volumes which they protect. If you plan to copy
individual RAR and REV files to some removable media, you need to take it
into account and specify RAR volume size by a few kilobytes smaller
than media size.</p>

<P>WinRAR reconstructs missing and damaged volumes either when clicking
on .rev file, or when using <A HREF="HELPCmdRC.htm">rc</A> command
or automatically, if it cannot locate the next volume and finds the
required number of .rev files when unpacking.</P>

<P>You may use "Recovery volumes" option of <A HREF="HELPGetArcAdvanced.htm">
Archive name and parameters</A> dialog or the similar option in <A
HREF="HELPCommandsProtect.htm">Protect archive</A> command to create
recovery volumes. In the <A HREF="HELPCommandLineSyntax.htm">command
line mode</A> you may do it with <A HREF="HELPSwRV.htm">-rv</A> switch
or <A HREF="HELPCmdRV.htm">rv</A> command.</P>

<P>Original copies of damaged volumes are renamed to *.bad before
reconstruction. For example, volname.part03.rar will be renamed to
volname.part03.rar.bad.</P>

</BODY>
</HTML>
